sophie heinz gsi helmholtzzentrum and justus-liebig-universität gießen
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Sophie Heinz
GSI Helmholtzzentrum and
Justus-Liebig-Universität Gießen
Fusion and Transfer Reactions in
Heavy Collision Systems with
Stable and Radioactive Beams
valley of β-stability
B p = 0
discovered arGSI - SHIP
Neutron number
Pro
ton n
um
ber
X + Pb,Bi
48Ca + X
Bp = 0
valley of β-stability
discovered atGSI - SHIP
The Heaviest Known Nuclei
Binding energy of a nucleus in the liquid drop model (Weizsäcker formula):
5
2
3/123/22/
),( BA
AZaAZaAaAaAZB ACSV
Condensationenergy
Surfaceenergy ES
Coulomb-energy EC Asymmetry energy
ES EC
deformation
V fissionbarrier Bf
for Z2 / A > 50 → Z > 100
Superheavy nuclei:
Bf = 0
What is a „superheavy“ nucleus ?
268106162
298114184
Quadrupole deformation β2
LD
Pote
nti
al energ
y /
MeV
LD + shell
25098152
Superheavy Nuclei:
Bfission = Eshell + Epair
Shell correction energies in the macroscopic-microscopic model
Fission Barriers of Superheavy Nuclei
Where are the next shell closures?
Macroscopic-microscopic models
A. Sobiczewski et al., 1995
P. Möller, 1995
114
114
S. Cwiok et al., 1998
Sky
rme-
Ha
rtre
e-F
ock
114
120
120
126
126
Relativistic mean field models
184
K. Rutz, W. Greiner et al., 1997
108
„Cold“ and „Hot“ Fusion Reactions
Cold Fusion → doubly magic target nuclei: Pb, Bi; E*(CN) = 10 – 20 MeV; evaporation of 1 – 2 neutrons;
up to now successful for Z ≤ 113
Hot Fusion → actinide targets (U, Cm, …) and 48Ca projectiles; E*(CN) = 30 – 40 MeV; evaporation of 3 – 4 neutrons;
up to now successful for Z ≤ 118
Synthesis of Superheavy Nuclei in Fusion Reactions
ER cross-section:
The Fusion Process in Heavy Systems
FUSION
TRANSFER, QUASI-FISSION
Nuclear Molecule
Compound Nucleus (CN)
EvaporationResidue (ER)
FUSION-FISSION
FissionFragments
survival CN captureER P P
1 pb corresponds to 1 nucleus per week
102 104 106 108 110 112 114 116 1181E-15
1E-14
1E-13
1E-12
1E-11
1E-10
1E-9
1E-8
1E-7
1E-6
Cro
ss-s
ect
ion / b
arn
Proton Number
1 pb
Cold fusion(X + Pb, Bi)
Hot fusion(48Ca + X)
Evaporation Residue Cross-sections for Cold and Hot Fusion Reactions
Evaporation Residue Cross-sections
5 · 1012 / s
29 ms
406 ms
1
2
sf
3
49 s
6.3 s
Z=116
„stop detector"
SHIP: G. Münzenberg Detector: S. Hofmann
single isotope identificationvia alpha decays
v ~ E/B
Δv/v = 0.1
The Velocity Filter SHIP at GSI
100 / s
Separation + Single Event Identification
Synthesis of superheavy nuclei at SHIP
The reaction 48Ca + 248Cm → 296116* (2010)
9.927 MeV, 0.58 s
10.625 MeV, 13 ms
9.184 MeV, 32 s
9.818 MeV, 1.9 s
10.533 MeV, 57 ms
9.315 MeV, 0.25 s
9.707 MeV, 4.0 s
10.029 MeV, 0.28 s
TKE = 213 MeV, 20 s
4
3
2
1
3
2
1
2
1
TKE = 213 MeV, 94 ms
TKE = 210 MeV, 34 s
293 116
289114
285Cn
281Ds
277Hs
293116
289114
285Cn
281Ds
292116
288114
284Cn
4n 3n 3n
10.502 MeV, 20 ms
4 chains 1 chain 1 chain
agree well with earlier data from Dubna
SHIP
Dubna
σ(293116)/pb
0.9
1.1
+2.1- 0.7
+1.7- 0.7
σ(292116)/pb
3.4
3.3
+2.7-1.6
+2.5-1.4
S. Hofmann et al., EPJ A 48: 62
S. Heinz et al., EPJ A 48: 32
observation of an α-branch in 281Ds
Study of Transfer Reactions at SHIP
N-rich nuclei at N = 126presently produced in fragmentation reactions
N-rich superheavy nuclei not reachable in fusion reactions
126
184
114
82
► Transfer reactions as a means to proudce new neutron-rich (super-)heavy isotopes
► Transfer reactions as first step to fusion
Study of Transfer Reactions at SHIP
48Ca + 238U at 4.90 MeV/u
5000 6000 7000 8000 9000 100000
1000
2000
3000
4000
5000
At-21
7Po-
216
Rn-
220 F
r-22
1
Ra-
224
Po-
212
Po-
213
At-21
5
Fr-21
9
Po-
214
Rn-
218
Ra-
220
Ra-
221
counts
/ 10 k
eV
alpha energy / keV
Ra-
222
550 600 650 7000
100
200
300
400
coun
ts / k
eV
Gamma energy / keV
β–
XAZ
Y
AZ+1
126
82
130
134
138142
146
150
84
86
88
90
92
80
78transfer products observed at SHIP
??
Isotope ID via α- or gamma decays
→ population of n-rich isotopes
Study of Transfer Reactions at SHIP
64Ni + 207Pb → Study of the capture process
survival CN captureER P P
Transfer
Transfer
Fusion
excitation functions of cold fusion reactions with Pb targets
Study of quasi-fission and fusion-fission
survival CN captureER P P
U(r
,Z,N
,L)
/ M
eVr / fm
232Th + 250Cf
A 1–A 2
/(A 1+A 2
)R
VNN
RDNS
nucleus-nucleus potential potential energy surface
→ potential energy landscape determines the preferred evolution paths of the nuclear system
Study of quasi-fission and fusion-fissionT
KE
/ M
eVyi
eld
/ re
l. un
its
mass number
E* = 35 MeV E* = 40 MeV E* = 46 MeV E* = 56 MeV
courtesy: Y. Itkis et al.
36S + 238U → 274Hs (Z = 108)
survival CN captureER P P
→ experiments in Dubna, JYFL, … (E. Kozulin et al.)
→ since 2012 also at GSI (E. Kozulin, S. Heinz et al.) CORSET setup
The CORSET Spectrometer
rotatable
Si stop detectorTOF(MCP detectors)
0.5 – 1 m
▪ time resolution: < 150 ps (ΔTOF/TOF ≈ 2 %)
▪ atomic mass from TOF and E (≥ 3 units for very heavy nuclei)
ΔΩ ≈ 50 msr
Si detector
TOF detector
The CORSET Spectrometer
CORSET setup at GSI
1 m
Penningtrap• mass selective• T1/2 > 100 ms
• m/Δm > 106 - 107
Time-of-Flight spectrometer• broad-band• T1/2 > 10 ms
• m/Δm > 105
stopping cell
(T. Dickel, W. Plaß et al., JLU Gießen)
Isobaric Identification through precision mass measurements
Study of other Techniques for Isotope ID
The MR-TOF-MS
DifferentialPumpingSection
Injection Trap System
Time-of-FlightAnalyzer
Ion GateIsochronous
SEM
Post-AnalyzerReflector
Gate Detectors
10-8 mbar
10-4 mbar
10-2 mbar
10-6 mbar
Kinetic Energy750 eV
W. Plass, T. Dickel et al., Univ. Gießen and GSI
ion catcher(cryogenic)
mass filterbuncher
MR-TOF-MS
Fusion Reactions with RIBs
actinide targets
Pb, Bi targets
radioactive beams
→ access to neutron-rich superheavy nucleibut: present beam intensities are too low
106 107 108 109 1010 1011 1012
100 b
10 b
100 pb
10 nb
100 nb
1 b
beam particles per second
1 nb
Required Beam Intensities
Required beam intensities to obtain 10 events per day at the given cross-section
500 μg / cm2 targets
fusion
Z ≥ 102
transfer, quasi-fission, fusion-fission
requires separator
Possible Experiments with RIBs
Study of transfer, quasi-fission and fusion-fission
in very heavy systems
Production of new n-richisotopes in deep inelastic
transfer reactions
Study of reactioncross-sections as function of the
projectile neutron number
Required beam intensities: > 107 / s
Required beam energies: ≥ 4 MeV / u
Summary
► We perform experiments in the region of the heaviest nuclei: ● Synthesis of superheavy nuclei in fusion reactions ● Study of related processes like capture, quasi-fisison, fusion-fission etc. ● Investigation of different reactions to produce new heavy isotopes
► Experimental setups: ● Separators for reactions with very low cross-sections: σ < 1 μb ● TOF–E–spectrometer for reactions with σ > 1 μb ● Multiple reflection TOF spectrometer plus injection system for separation and isotope ID
► Present RIB intensities do not allow for synthesis of SHN in fusion but allow for the study and application of quasifission, fusion-fission etc.
Collaborating Institutes
– GSI Helmholtzzentrum, Darmstadt
– Justus-Liebig-Universität Gießen
– Joint Institute for Nuclear Reactions, Dubna, Russia
– RIKEN Nishina Center for Accelerator-based Science, Japan
– Japan Atomic Energy Agency
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